1. Field of Invention
The present invention relates to a flip-chip light emitting diode with high illumination intensity and high power by which the operational voltage of the light emitting diode can be reduced, the lumen/watt can be enhanced and the high light emitting efficiency can be maintained effectively.
2. Related Art
In the recent years, light emitting diode with high illumination intensity made of nitrides and phosphides have been developed which not only can emit red, blue and green light, but also various colors of light and white light.
Conventional light emitting diode is directly made as a light emitting diode epitaxial structure disposing on a substrate material. Cathode electrode and anode electrode are made on the side of the light emitting diode epitaxial structure and the side of the substrate material respectively. Even though such structure has better electric current distribution effect, it is difficult to reduce the operational temperature of the light emitting diode because the light emitting layer is disposed relatively far away from the package base and the impedance of heat conduction is relatively high. Therefore, it becomes an obstacle to develop light emitting diode with higher power. Consequently, flip-chip light emitting diode has been developed in the recent years.
In a flip-chip light emitting diode, a p-type semi-conductive layer and a n-type semi-conductive layer of the light emitting diode epitaxial structure are exposed on the same side of the light emitting diode epitaxial structure, so that a cathode electrode and an anode electrode can be made on the same side of the light emitting diode epitaxial structure. Therefore, flip-chip packaging can be employed to directly stack the light emitting diodes installed with the cathode electrode and the anode electrode on a package solder. Thereby, conventional metal wire bonding is not required and the package area can be reduced effectively. At the same time, the thermal resistance of the light emitting diode can be reduced because the light emitting layer is closer to the package base. As a result, the reliability of the light emitting diode can be enhanced substantially.
Even though flip-chip light emitting diode can provide some advantages in packaging, because the p-type semi-conductive layer and the n-type semi-conductive layer of the light emitting diode epitaxial structure are exposed on the same side of the light emitting diode epitaxial structure, and the electric conductivity of the semi-conductive layer is relatively poor; electric current can not be evenly distributed from the connecting points effectively and the density of electric current of some areas inside the light emitting diode is too high. As a result, the overall illumination intensity and the life expectancy are reduced and the light emitting efficiency of the light emitting diode is affected.